Jim couldn't find a job, so he opened a medical clinic. He put up a sign reading, "I'll cure you for $500 or else give you $1,000."
A doctor thought this looked like an easy way to make $1,000 so he made an appointment. The doctor complained, "I can't taste anything."
Jim said, "Nurse, bring bottle 22 and administer three drops to this patient." She did and the doctor spluttered, "This is gasoline!"
"Congratulations! Your taste is back. That'll be $500." The doctor was pissed, but paid.
A couple of days later, he went back to recover his money. "I've lost my memory." Jim said, "Nurse, bring bottle 22 and administer three drops to this patient."
The doctor shouted, "No! That's gasoline!"
"Congratulations! Your memory is back. That'll be $500."
The doctor vowed revenge. After a few more days, he returned. "My eyes are going bad. I can't see!"
Jim said, "I have no medicine for this. Here's $1,000." The doctor counted the money and complained, "But this is only $500!"
Jim said, "Congratulations! Your vision is back! That'll be $500!"